1. Field of the Invention
Embodiments of the invention generally relate to an apparatus and method for cleaning a bevel of a substrate after a semiconductor processing step has been conducted on the substrate.
2. Description of the Related Art
Metallization of sub-quarter micron sized features is a foundational technology for present and future generations of integrated circuit manufacturing processes. More particularly, in devices such as ultra large scale integration-type devices, i.e., devices having integrated circuits with more than a million logic gates, the multilevel interconnects that lie at the heart of these devices are generally formed by filling high aspect ratio, i.e., greater than about 15:1, interconnect features with a conductive material, such as copper. Conventionally, deposition techniques such as chemical vapor deposition (CVD) and physical vapor deposition (PVD) have been used to fill these interconnect features. However, as the interconnect sizes decrease and aspect ratios increase, void-free interconnect feature fill via conventional metallization techniques becomes increasingly difficult. Therefore, plating techniques, i.e., electrochemical plating (ECP) and electroless plating, have emerged as promising processes for void free filling of sub-quarter micron sized high aspect ratio interconnect features in integrated circuit manufacturing processes.
In an ECP process, for example, sub-quarter micron sized high aspect ratio features formed into the surface of a substrate (or a layer deposited thereon) may be efficiently filled with a conductive material. ECP plating processes are generally two stage processes, wherein a seed layer is first formed over the surface features of the substrate (generally through PVD, CVD, or other deposition process in a separate tool), and then the surface features of the substrate are exposed to an electrolyte solution (in the ECP tool), while an electrical bias is applied between the seed layer and a copper anode positioned within the electrolyte solution. The electrolyte solution generally contains ions to be plated onto the surface of the substrate, and therefore, the application of the electrical bias causes these ions to be plated onto the biased seed layer, thus depositing a layer of the ions on the substrate surface that may fill the features.
Once the plating process is completed, the substrate is generally transferred to at least one of a substrate rinsing cell or a bevel edge clean cell. Bevel edge clean cells are generally configured to dispense an etchant onto the perimeter or bevel of the substrate to remove unwanted metal plated thereon. The substrate rinse cells, often called spin rinse dry cells, generally operate to rinse the surface of the substrate (both front and/or back) with a rinsing solution to remove any contaminants and/or residual chemicals therefrom. Further, the rinse cells are often configured to spin the substrate at a high rate of speed in order to spin off any remaining rinsing fluid droplets adhering to the substrate surface after the rinsing process is complete. Once the remaining fluid droplets are spun off, the substrate is generally clean and dry, and therefore, ready for transfer from the ECP tool to another tool, such as a chemical mechanical polishing tool for subsequent processes.
However, conventional bevel clean chambers or cells present several challenges and/or disadvantages. For example, conventional bevel cleaning cells have been prone to etchant “splash back”, which is generally defined as when chemicals used in the removal process (which are generally very acidic) splash or are otherwise caused to return to the production surface of the substrate. Splash back can occur from the physical deflection of fluid from the substrate surface upon application of the fluid to the substrate surface (generally in the bevel region), or alternatively splash back may be caused be the airflow generated by the rotation of the substrate not being adequately controlled and reversing flow direction toward the substrate center.
Further, conventional bevel clean chambers and cells have difficulty accurately centering substrates for processing without bowing or even breaking the substrate. This is critical to advancement of plating processes not only for reduction in substrate breakage, but also for accuracy of chemical application. As circuit densities increase, maximization of the available surface area on the substrate becomes important. Improper or inaccurate substrate centering before application of a bevel cleaning solution can substantially limit the available surface area.
Therefore, there is a need for an improved bevel clean chamber capable of minimal splash back and accurate centering.